動態加載下的等效單軸應變與 應力材料組成模型;Equivalent Uniaxial Strain And Stress Material Constitutive Model Under Dynamic Loading

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Title:	動態加載下的等效單軸應變與應力材料組成模型;Equivalent Uniaxial Strain And Stress Material Constitutive Model Under Dynamic Loading
Authors:	顏昱丞;Yen, Yu-Cheng
Contributors:	土木工程學系
Keywords:	等效單軸應變;非線性分析;混凝土動態加載;材料破壞模型;冰塊材料;動態模型;劣化模型;Equivalent uniaxial strain;nonlinear analysis;dynamic loading of concrete;material failure model;ice material;dynamic model;deterioration model
Date:	2018-11-27
Issue Date:	2019-04-02 14:06:50 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究提出的動態加載下的三維等效單軸應變與應力組成模型，目的是研究混凝土材料動態加載下的行為，因為日常生活中結構物大多數都是受到動態加載如地震、撞擊和爆炸等現象。本研究引用Darwin & Pecknold提出的等效單軸應變概念，分離材料多軸受力時的柏松比效應(Poisson’s ratio)，且透過單軸行為預測多軸行為，在本研究的數值模擬方法中以全量應變做計算，而非傳統塑性力學中分為塑性應變和彈性應變，簡化了混凝土在塑性行為分析中許多積分及複雜的數學計算。材料模型中主要分為兩個部分，分別為材料破壞模型(Ultimate failure model)，及單軸應力應變曲線(Uniaxial stress strain model)。單軸應力應變模型採用Saenz所提出的單軸應力應變公式，此公式僅需定義極限強度參數即可描述混凝土行為中之硬化段與軟化段，在數值模擬的使用上相當簡潔且方便。本研究提出動態材料破壞模型，採用Menetrey和Willam所提出之三參數破壞準則與Balan等人所提出的帽蓋模型結合形成了Close-Menetrey-Willam模型。並透過動態增量因子(Dynamic Increase Factor)使破壞模型擴張，建立不同應變率加載狀態下之動態破壞模型，將不同時刻下之應力狀態於動態材料破壞模型上定義當前時刻之極限強度參數(Ultimate strength parameters)。本研究提出老劣化模型，採用杜建民提出的劣化強度公式與Close-Menetrey-Willam模型結合使得模型縮減，建立不同損傷程度下的劣化破壞模型，定義在劣化模型上的極限強度參數，將其帶入單軸應力應變模型中進行預測。本研究之模型維持一貫之數值計算流程，只需修改動態材料破壞模型以及單軸應力-應變破壞模型即可，本研究之數值算例分別驗證了混凝土高應變率和低應變率加載的情形、冰塊低應變率加載的情形且考慮不同溫度下的冰塊應變率加載和混凝土硫酸鹽劣化的加載。 ;This research presents a dynamic three-dimensional constitutive model of material equivalent uniaxial strain and stress. The purpose is to study the behavior of concrete materials under dynamic loading, because most of the structures in daily life are subject to dynamic loading such as earthquakes, impacts and explosions. This research uses the equivalent uniaxial strain concept proposed by Darwin & Pecknold to separate the Poisson′s ratio of multi-axial forces. The equivalent uniaxial strain is a fictitious material index which is invented to compute the parameters such as material stiffness modulus and Poisson’s ratio. This research proposes a dynamic material failure model, which combines the three-parameter failure criterion proposed by Menetrey and Willam with the cap model proposed by Balan et al. to form the Close-Menetrey-Willam model. The dynamic failure model is expanded by the DIF (Dynamic Increase Factor). The dynamic failure model under different strain rate loading states is established, and the stress state at different moments on the dynamic material failure model to define the ultimate strength parameters at the current moment. Using the uniaxial stress-strain model proposed by Saenz, this formula only needs to define the ultimate strength parameters to describe the hardened and softened sections in concrete behavior. It is quite simple and convenient to use in numerical simulation. This study proposes a concrete deterioration model. The combination of the concrete deterioration strength formula proposed by Du Jian-min and the Close-Menetrey-Willam model, establishes a deterioration model with different damage levels, defines the ultimate strength parameters of deterioration model. The numerical examples in this study verify the high strain rate, low strain rate loading of concrete, low strain rate loading of ice, the low strain rate loading of ice at different temperatures and concrete deterioration.
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